The present invention relates to a high-frequency heating apparatus of the composite type comprising a heater, and more particularly to an automatic high-frequency heating apparatus in which automatic operation is effected by the use of a humidity sensor or a gas sensor to provide alternate heating with an electric heater and a microwave heater.
The alternate heating of an object to be heated from the outside and inside thereof at the same time is generally called "pair heating", "combination heating" or "mixed heating" and finds wide application in what is called a microwave oven range, namely, a high-frequency heating apparatus of the composite type comprising an electric heater and a magnetron heater. The alternate heating is capable of cooking a part of oven heating food within a short time without any preheating process. This alternate heating permits speedy cooking of roast beef, roast pork, pound cake, etc., so that it has been highly valued as a method specifically utilizable by the microwave oven range.
The alternate heating process, however, has a disadvantage in that the quantity of the object to be heated is limited. In oven heating, food is baked in an enclosed oven chamber over a predetermined time period with the temperature in the oven chamber kept at a predetermined level, and generally the length of time necessary for completing the oven heating is almost not affected by variations in the quantity of food. In the case of microwave heating, on the other hand, energy is absorbed directly into the food, and therefore the heating time changes with the quantity of food. Despite the fact that alternate heating has the advantages of making preheating peculiar to oven heating unnecessary and shortening the completion time length, it is accompanied by the disadvantage that the heating time depends on the food quantity. Thus, in conventional alternate heating which is controlled by time and temperature, restrictions on the food quantity have been unavoidable.
The present invention is intended to obviate the above-mentioned disadvantage of the prior art, and the object thereof is to provide a high-frequency heating apparatus capable of automatic cooking by alternate heating without restrictions on the food quantity.